The work in this proposal involves studies of the genetically determined influence of the kidneys in the development of hypertenson (HT) in two unique strains of rats evolved at Brookhaven: one strain (S) rapidly develops severe HT after a variety of insults to which the other strain (R) responds only mildly, if at all. Interstrain renal transplants chronically modify the blood pressure of the recipients: kidneys from the hypertension-resistant rats generally have an antihypertensive effect whereas kidneys from the hypertension-prone strain have a prohypertensive effect. The specific influence of the kidney will be assessed in established renal hypertension by transplanting either an R or an S kidney; the influence of mild injury to the homograft (by brief salt-feeding to the donor animal) on the subsequent course of blood pressure will be studied; the influence of renal medulla transplants from R or S rats on the BP of S rats with salt-HT will be assessed; the effect of cadmium on the BP of R and S rats will be initiated; on-going studies of the effect of renal parenchymal injury induced by pyelonephritis and anti-kidney serum nephritiswill be concluded. Finally, if time and personnel are available, we will study the role of pads of musculo-elastic hyperplasia, observed at sites of arteriolar branching in the kidneys of S rats, in the pathogenesis of the malignant HT that develops in S rats on NaCl. These pads might function as "micro-Goldblatt" clamps. Correlations between the frequency of these pads and HT will be made in R, S, F1 and F2 rats.